This invention concerns a differential gear unit for motor vehicle drive axles having a positive differential lock which comprises a jaw clutch plate which is non-rotatably connected to the housing for the differential gear (differential case) but is axially movable with respect to the same. The jaw clutch plate cooperates with a jaw clutch counterplate which is mounted non-rotatably and axially fixed on the associated wheel drive shaft. The jaw clutch plate also serves as an armature for an electromagnet formed as a magnetic ring, which can be switched on and off manually.
International Patent Application WO 86/01467 discloses a steering drive axle, that is, the front axle of an automobile which has a differential lock. The operation of the differential lock consists essentially of a lock differential and a jaw clutch plate connected thereto, which by means of an electromagnetic positioning element connects the wheel drive shaft with the driven part of the lock differential so long as a presettable deflection angle stop value is attained or exceeded. The switching in and out of the known lock differential is thus deflection angle dependent.